Improper Connections between ElectricPlasma Host and NDG7475?

[Pr1m4lcur5e]

So, to begin, I am using ElectricPlasma's Bronze and Copper Host. I plan on putting an NDG7475 in it, and am using the AWP18650 batteries.
Upon first trying it out, I found that the batteries were larger than 18650s with no protection, and did not fit into the host nicely.
Thus, I sent it back to EP and he was so kind as to machine a new piece to go on the end so that the batteries would fit.
In addition, I messed up the initial contact board and tore the positive lead from the X-Drive. He was also willing to resolder that connection and make a new contact board.

Having received the laser host yesterday, I was quite excited to finally put it back together, after having practiced with epoxy to ensure that I don't repeat my past mistake with the contact board.
So I pressed the module into the heatsink, and then hooked the red lead into the nut and bolt of the contact board,
carefully and thinly coating the surface of the nut and bolt assembly with epoxy in hopes of preventing a short.
After that, I used the pinch method as shown to me by EP and BobMc, wrapping the black lead around the base of the contact board, making sure it doesn't touch the bolt or red wire.

And then I placed the board into the heatsink. From there, I got my batteries and some conductive magnetic spacers so the batteries would fit perfectly into the host.
Excited, I put them together without applying adhesive to the heatsink in fear that something would go wrong and I would have to pull it apart.
Despite fitting perfectly, I was able to see the green light for about a split second before it turned off.
I am hoping the diode has not been damaged, as I have been able to reproduce this incident a few times now. I'm not really sure I was able to do so, but I think that the diode still works, since it did all the times before.
So now I am here, wondering, where did I mess up and make an improper connection for this to happen? I've tried searching the forum, but I've been unable to find another incident like this. Perhaps I just missed it. Sorry for the wall of text, pics coming soon. Thanks everyone.

 

[Pr1m4lcur5e]

Here are some pics, sorry if I did something wrong, hopefully they got resized properly.

 

[Pr1m4lcur5e]

I think these are resized a bit better. Sorry about that, if anything else is required, please just tell me.

 

[paul1598419]

Maybe I'm missing something, but where is the negative connection for the driver located? If I had to guess from what I've seen, I'd say that is your problem. It should be continuous from the heat sink to the switch, where it is made and broken to turn the laser on and off.

 

[Pr1m4lcur5e]

The negative connection from the driver is wrapped around the inside of the contact plug, so it is not visible from the outside. Picture credits to EP, but It looks sort of like this:









It's a bit late where I am right now, but I'll retry with the negative connection tomorrow. If that's it, then it certainly would be an easier fix than I thought. Maybe I just didn't get it quite tight enough. Thanks paul1598419, your feedback is greatly appreciated.

 

[paul1598419]

This is a press to connect negative leg and could be the poor connection you are experiencing. It is difficult to troubleshoot a problem with photos online. It is my best guess with what you've shown me so far.

 

[ElectricPlasma]

Just had a thought, have you tried bypassing the tailcap? Maybe the solder came loose or something. Also have you tested continuity, and have you tried a bench power supply or another power source?

I would've PMed you this but giving this thread a bump isn't such a bad idea.

Edit: also make sure it's not because of a short, you can use a multimeter at the end cap to test that (ammeter, should spike with no laser output if shorted, open/terminate the circuit immediately if this is the case). Like Paul said, it can be difficult to troubleshoot with just photos.

 

[Pr1m4lcur5e]

I've tried using different batteries, with no success. I don't know for sure what to do when testing with a multimeter. I've heard that testing with a multimeter can be dangerous without a dummy load? I'm currently trying Paul's suggestion, but it doesn't seem like that is the case. Thanks, I understand how it can be difficult to troubleshoot based just on pictures, as they can't provide everything that needs to be known.

 

[paul1598419]

If it has a tail cap switch, you can remove that and use an alligator clip lead to jump the battery to the case of the host. That would eliminate the switch as the problem. Just make sure you push the battery(ies) into the host to make good contact when you do.

 

[Pr1m4lcur5e]

Eureka!!!! Thanks Paul and EP, that seems to have done it! The alligator clip suggestion made the laser turn on to full brightness! So then that means something must be up with the tailcap's connection?

 

[paul1598419]

Bingo!

 

[diachi]

I've tried using different batteries, with no success. I don't know for sure what to do when testing with a multimeter. I've heard that testing with a multimeter can be dangerous without a dummy load? I'm currently trying Paul's suggestion, but it doesn't seem like that is the case. Thanks, I understand how it can be difficult to troubleshoot based just on pictures, as they can't provide everything that needs to be known.

The dummy load is only required when testing the the diode driver's output current to make sure that it's at the correct current.

A dummy load is electrically similar to a laser diode but is A) cheaper and B) much less likely to fail in the event that there's a current spike while adjusting the driver/current is set too high initially/something else goes wrong. Laser diodes are very sensitive to noise/voltage spikes/ESD and so on. A dummy load prevents you from accidentally killing your laser diodes when setting up a driver. :beer:

Glad to hear you got it working! Sounds like something is messed up in the tail cap, loose connection or bad switch. You should be able to take it apart and repair the faulty connection/switch. I'll leave the "how to" for ElectricPlasma seeing as he's familiar with the design.

 

[Pr1m4lcur5e]

I know that a picture doesn't do too much to help me, but this is what the tailcap looks like:

 

[paul1598419]

Since ElectricPlasma built it, he would know more than I. But, my best guess is either the solder connection to the cap is cold (bad), or the switch has failed. The solder connection there is difficult to make to the cap as heat is transferred to the entire cap. You can see the switch contact is the metal piece in the black plastic. If that doesn't make a solid connection, it can cause that to happen. if that is the problem, you could soldert a spring to the switch contact and that would make the connection for you.

 

[Pr1m4lcur5e]

So I first tried resoldering to the cap, which did not help. Then I tried soldering a spring to the switch, which didn't help either. And I didn't see any change in my multimeter, not even a beep, while testing for continuity. My best guess is that the switch isn't working properly. Would I be wrong to think so?

 

[paul1598419]

From what you've said, I would think bad switch too. It happens more often than you would think. Some switches are rated for higher currents than others and this is often the cause of a failure.